Chemotaxis is the process by which bacteria swim to higher concentrations of attractants or lower concentrations of repellents. Peritrichous bacteria alternatively swim smoothly and tumble, whose effect is random reorientation for the next swim. Chemotaxis occurs by increasing propensity to tumble when bacteria are headed in the "unfavorable" direction and by increasing propensity to swim when the bacteria are headed in the "favorable" direction (such as toward higher attractant concentrations). We are chiefly interested in elucidating the biochemical events that underlie chemotaxis in Bacillus subtilis and isolating and studying the factors involved. It appears likely that swimming and tumbling is regulated by changing internal free Ca ions ion concentration. Accordingly, we are seeking to identify Ca binding proteins, particularly those present in wild type but missing in chemotaxis and motility mutants. Adaptation to attractant involves methylation of a membrane protein which, we hypothesize, changes its affinity for Ca ions ion. We are in the process of identifying and studying the pertinent methyltransferase from Bacillus subtilis and its methylated product.